In general, a wafer being processed in lithography has one or more round edges, while imprint fields on the wafer are rectangular. As a result, when processing the edge of the wafer, portions of the rectangular fields extend off of the edge of the wafer. This gives rise to many issues when attempting to maintain a clean and efficient fabrication process.
In many cases, it is possible that a field actually contains an array of usable chips that are much smaller than that field size, and such a smaller array may be processed on the edge of the wafer in order to maximize the use of the wafer area. Conversely, in some lithographic processes it may be desirable to process the edge with the goal of assuring edge conformity, and not necessarily to yield usable chips. Edge conformity may be important because many fabrication processes rely on the full wafer having patterning or material extending to the edges. When edge conformity is lacking, it can lead to problems in subsequent processes like etching, for instance, where the recipes are tuned to having a full wafer. In some cases, nonconformity may become worse with each subsequent step in the fabrication process.
Imprint-based systems, and particularly nanoimprint systems, are now being utilized in advanced lithography processes because advances in imprint-based technology have yielded resolution capabilities superior to that of projection systems. These systems generally function by dispensing resist onto a die area and physically stamping the area with an imprint template. However, problems with these systems may occur because in order to print edge die, the imprint template must extend off the edge of the wafer. This causes problems when balancing the forces applied for the physical contact due to the fact that portions of the imprint template are in contact with a semiconductor wafer, while other portions of the template extend off of the edge of the wafer and do not contact anything. Moreover, issues arises at the wafer edge when part of the template is in contact with the fluid on the wafer, and part of it is not in contact with anything. This border is a source or particles which can easily contaminate the template. As such, even after one contact, it is very likely that particulates and debris from the edge of the wafer will stick on the template, rendering the template insufficient for further use absent a cleaning process. Accordingly, current imprint-based systems do not provide the ability to process edge areas in a manner which yields sufficient edge conformity without causing significant time and resource complications.